These were crimes committed before becoming president, not acts during their presidential term. He defrauded the American people in order to promote himself for office.

While I certainly do not believe it is infinite, there is something to the Trump/Republican argument that the POTUS shouldn't have to weigh being prosecuted after they leave office in every decision they make. I would expect some kind of leniency if there is a strong belief people think they were acting in the best interest of the country. Which certainly would not have been true about Watergate, but as others have pointed out, he was pardoned before he could be charged.